The present invention pertains generally to an apparatus for providing access to a living body. More particularly, the invention relates to an improved vascular access device or introducer set used to obtain percutaneous canalization of blood vessels to facilitate the passage of catheters through tissue and vascular walls while eliminating the need to thread multiple components over a guidewire.
The purpose of an introducer set is to place a section of tubing, for example an introducer sheath for a catheter, into a vessel, or other body part, that has a sufficiently large and rigid inner diameter to facilitate insertion of other proportionately large tubes, catheters, or other instruments into said vessel or body part. An introducer set commonly contains a small diameter device with a sharp tip, commonly a hypodermic needle, so that the introduction can start with a relatively small, easily produced, puncture wound, minimizing trauma to the involved tissues. This small puncture wound is then expanded, ideally by stretching rather than tearing or cutting the involved tissues, with a tapered dilator. The wall thickness of the introducer sheath must be as small as possible, minimizing the outside diameter of the introducer sheath to minimize the trauma to the body tissues involved while maximizing the size of the inside of the opening for insertion of other devices.
One classical procedure for preparing an opening to introduce devices into a blood vessel, a body opening or other body duct is a multi-step procedure involving a number of independent devices and steps. The following steps set forth a conventional introducer set and method of use.
1) First, a hypodermic needle with glass or clear or translucent plastic syringe attached, is inserted into a vessel. When the pressure in the syringe is lower than the pressure in the vessel, blood will shoot up the needle and into the syringe where it can be observed by the operator. Observed features, such as color and rate of flow of blood, confirm that a blood vessel has been hit, and indicate the type of vessel. The ability to observe the blood is a necessary part of the procedure for blood vessel access or, for example, access to a cyst or duct.
2) Next, while holding the needle in place, the syringe is disconnected from the needle. At this point, blood can flow, or squirt, out of the proximal opening of the needle and/or air can be sucked into the needle if the pressure in the body vessel should fall below ambient pressure. This latter effect can occur in a vein during normal inspiration, when the veins often collapse under negative pressure created in the venous system by the depression of the diaphragm.
3) As quickly as possible, to minimize the above effects, a guidewire is inserted into the proximal end of the needle, effectively and approximately closing the hole and stopping fluid or air flow. The guidewire is then threaded well into the vessel. The guidewire must be flexible to turn the corner from the needle-stick track, which enters the vessel at an acute angle.
4) The needle is then removed by pulling the needle backwards over the full length of the guidewire while simultaneously holding the guidewire in place.
5) Next a dilator, with an introducer sheath slidingly positioned over it, is threaded onto the proximal end of the guidewire. The distal tip of the dilator has an inner diameter just large enough to slip over the guidewire with little friction. The outer diameter of the distal tip of the dilator is only slightly larger than the inner diameter, creating a relatively smooth transition from guidewire to dilator. The outer diameter of the dilator is tapered to a larger dimension, the taper occurring over a distance of about one or more centimeters back from the tip. The distal tip of the introducer sheath is positioned just proximal to the proximal end of the taper. As the dilator-sheath combination is pushed forwards, the tip follows the guidewire into the vessel, and the following tapered outer dimension dilates the hole through the body and the wall of the vessel, stretching the inner diameter of the vessel itself to a larger than normal diameter. The dilator must also be flexible enough to turn the corner from the needle track to the long axis of the vessel. However, a relatively large force may be required to push the dilator through all the intervening tissues and to expand the vessel diameter, so the dilator/guidewire combination must also have a proportionately large stiffness to prevent buckling. The distal end of the introducer sheath follows the dilator into the vessel. This sheath commonly has a constant inner diameter, just big enough to slip over the outer diameter of the dilator, and a constant-thickness thin wall. It must be flexible enough to pass from the body tissues outside the vessel, enter the vessel at an angle, and turn the corner to follow the long axis of the vessel. The force required again may be relatively large, but the dilator prevents buckling of the thin-walled, relatively flexible introducer sheath. Note that it would not be possible to insert the introducer sheath over the guidewire without inserting the dilator first because the required force would be great, the trauma to the tissues would be severe, and the stiffness of such a sheath would be inconsistent with the need for a flexible thin-walled device.
6) The dilator is then withdrawn, holding only the introducer sheath, and perhaps the guidewire, in place. The procedure is now complete. This introducer sheath permits repeated insertion and removal of useful devices of relatively large diameter, such as infusion catheters, balloon angioplasty catheters, angioscopes, etc. into the body and through the vessel wall without repeated trauma to vessel or intervening tissues.
The necessary threading of numerous components requires a large sterile field in which to work, is difficult to perform with just two hands, and permits blood spillage during much of the process. What is therefore needed is a system which eliminates the need for multiple threading to reduce the incidence of needle stick, the quantity of blood spillage, the time required to perform the procedure, and the sterile field required. The present invention satisfies these needs without requiring relearning of current puncture techniques. The present inventive device represents a single assembly which replaces the multiple components, each of which must be handled separately in the classical, conventional procedure. Additionally, the device of this invention can be used with ease by a single user, whereas the conventional method may generally require more than one person to handle the multiple components.
The inventive device described herein is a modified needle/catheter system whereby one inner element (i.e. a guidewire or other catheter) may be introduced into a modified needle or introducer from a position other than its proximal end in such a way that the needle or introducer may be removed for the most part non-coaxially. The device of the present invention would allow for the pre-loading of all elements prior to introduction of the assembly into the desired space or lumen (i.e. artery) and therefore reduce the time, skill and manpower necessary to thread the elements once the space has been entered. The device facilitates the introduction of catheters over a guidewire in the open surgical, laparascopic and percutaneous settings. Because the device is essentially a closed system, the risk of significant blood loss (arterial) or air-embolus (venous) during the introduction procedure is significantly reduced. The device may also allow the use of "hubbed" catheters in such situations where their use was previously prohibited (i.e. epidural anesthesia).
A preferred embodiment of this invention involves a slotted or slot-able needle, where the slot extends from a point on the body of the needle and extends towards the tip. The needle is then inserted through a tight fitting hole in the wall of a catheter and the slot oriented such that the inner lumen of the needle communicates directly with the proximal lumen of the catheter. This communication thereby allows an inner guide to be passed from the lumen of the proximal catheter to the lumen of the needle and out the needle tip. The tip of the outer catheter may be modified to fit closely to the outer aspect of the needle and may be tapered to facilitate introduction into the vessel. This outer catheter may be the primary catheter desired to be inserted into the vessel or it may be the dilator for an introducer catheter that is threaded coaxially upon its proximal end. A catheter may be generally defined as any device with a relatively flexible portion containing a lumen (i.e., a dilator, introducer catheter, or endoscope).